This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present disclosure that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admission of prior art.
Conventional image capture devices project a three-dimensional scene onto a two-dimensional sensor. During operation, a conventional capture device captures a two-dimensional (2-D) image of the scene representing an amount of light that reaches a photosensor (or photodetector) within the device. However, this 2-D image contains no information about the directional distribution of the light rays that reach the photosensor (which may be referred to as the light-field). Direction of incoming light, for example, is lost during such 2D acquisition and information like depth cannot be recovered for a single system. Thus, a conventional capture device does not store most of the information about the light distribution from the scene.
Light-field capture devices (also referred to as “light-field data acquisition devices”) have been designed to measure a four-dimensional (4D) light-field of the scene by capturing the light from different viewpoints of that scene. Thus, by measuring the amount of light traveling along each beam of light that intersects the photosensor, these devices can capture additional optical information (information about the directional distribution of the bundle of light rays) for providing new imaging applications by post-processing. The information acquired/obtained by a light-field capture device is referred to as the light-field data. Light-field capture devices are defined herein as any devices that are capable of capturing light-field data. There are several types of light-field capture devices, among which:                plenoptic devices, which use a microlens array placed between the image sensor and the main lens, as described in document US 2013/0222633;        a camera array.        
The light field data may also be simulated with Computer Generated Imagery (CGI), from a series of 2-D images of a scene each taken from a different viewpoint by the use of a conventional handheld camera.
Light-field data processing comprises notably, but is not limited to, generating refocused images of a scene, generating perspective views of a scene, generating depth maps of a scene, generating extended depth of field (EDOF) images, generating stereoscopic images, and/or any combination of these.
Hence, among others, a 4D Light-Field (4DLF) allows computing various re-focused images with adjustable depth-of-field, focalization distances and viewing positions. However, user experience is often limited to simple rendering on TVs or monitors, 2D computers and mobile displays.
It would be interesting to allow a user to visualize a personalized view (according to a given point of view, a user dependent depth blur . . . ) from the multiple directions and depth of field images that can be computed from a light field based acquisition system.
To this end, some academic works have focused on re-focalization, or on changing viewpoint direction from a light field image, such as Marc Levoy in “Light fields and computational imaging” IEEE Computer 39, no. 8 (2006): 46-55, and Ng Ren, et al. in “Light field photography with a hand-held plenoptic camera” Computer Science Technical Report CSTR 2, no. 11 (2005).
Some camera manufacturers such as Lytro® or Raytrix® also offer solutions for personalizing the image displayed to the user.
According to these techniques, interaction between the user and the display is offered by means of mouse pointing or by touching a tactile screen. For example, the user may point to an object in the scene, and the image displayed to the user will, in turn, show the selected object in focus.
It would be desirable to provide a technique for displaying a light field image that would enhance the interaction between the user and the light field content over the prior art. Notably, it would be desirable to provide such a technique, which would enhance the interaction with the light field content by optimizing the generation and use of viewpoint and/or refocusing parameters representative of user navigation in the light field image or video content.